Sin is Crouching at Your Door
by FestiveFerret88
Summary: So Cas looked, not just with his eyes, but with tendrils of his borrowed grace, reaching out and peering into the in-between spaces. And it was Dean. But not. There was no other demon burrowed into Dean's shape, but Dean's soul was twisted and cracked, wrapped around the Mark and curled through with darkness. This demon was his own. [Demon!Dean oneshot]


The heavy curtains kept light from leaking into the dingy hotel room which was all for the best considering no one should be able to see the state of the carpet. The room was cheap though, and it had a bed in it, which was all Castiel needed. He was deep in a dreamless sleep when a sudden sharp knock at the door pulled him back to consciousness.

"Just a minute," he called out gruffly, rolling out of bed and staggering over to open the door.

Cas wondered if he actually __was__ dreaming. It would be unusual, but so was his need for sleep and the constant painful catching in his chest.

"Dean," he managed to cough out. But it wasn't Dean.

"Heya, Cas." The Dean-like thing grinned at him. Then its eyes slipped lower and the grin turned into a smirk. Cas glanced down, realized his bathrobe was hanging open and folded it around himself, carefully, holding the soft fabric defensively against his chest.

"You're not Dean," he said carefully.

The thing's smile wavered a little. "Sure I am. Look at me, Cas." He certainly sounded like Dean, but Cas could see the roiling, black smoke of a demon curled up inside. The thing took a step towards him and Cas automatically stepped back, but it reached up and grabbed both of his shoulders and pulled him closer. "Really look at me."

So Cas looked, not just with his eyes, but with tendrils of his borrowed grace, reaching out and peering into the in-between spaces. And it was Dean. But not. There was no other demon burrowed into Dean's shape, but Dean's soul was twisted and cracked, wrapped around the Mark and curled through with darkness. This demon was his own.

"Dean," Cas repeated, this time twisted with concern. He reached up an unsteady hand and touched the other man's chest, letting a spark of grace alight on the end of his fingers. Dean's eyes immediately went black – the demon inside pressing up against them in its desire to get away from God's light. "What did you do?"

Dean blinked, took a deep breath, and the black subsided. "I died, Cas. But the Mark wouldn't let me go."

Cas opened his mouth to say something, but a hacking cough worked its way up his throat instead and he bent double, turning away from Dean to clutch at his chest. Dean gripped Cas's shoulder hard, keeping him upright and leading him to sit on the bed. When Cas met his eyes again the darkness had receded – replaced only with worry.

Dean glanced around, finally taking in the shabby room, the mussed sheets, Cas's lack of clothing. "What are you doing here?"

Instead of answering Dean's question, Cas asked one of this own. "How did you find me?"

"Well, if you ever stop using Clarence as an alias, I probably won't be able to," Dean chided gently.

Cas just stared at him. "I wasn't hiding."

"Okay," Dean replied, nodding. Then softly added, "What's wrong?"

"Borrowed grace." Cas ran a hand through his hair. "It's getting worse, Dean, I'm dying, I can feel it."

Dean paced a few short laps around the room, then tossed Cas his suit which lay discarded on the patchy armchair in the corner. Cas started pulling it on automatically, not thinking to ask why he should dress.

"Is there anything you can do?" Dean asked. Cas watched him carefully for a moment. It was unlike Dean to phrase it like that. He was usually swearing up and down that __they would find something,__ or __he would fix it__. This Dean sounded resigned, a little detached, but not uncaring. Cas wasn't sure how he felt about the change but the longer he was here in Dean's presence the less he looked like a black-eyed demon and the more he looked like his green-eyed human.

"No, there is nothing. My grace is gone, no other will help more than temporarily." Cas stood and finished buttoning his shirt, stepping closer and bringing Dean's random patterns around the small room to a halt. "I need to call Sam."

Dean grabbed his wrist before he could reach for his cell phone. "No. Leave Sam out of this." There was a tense breath where Cas considered calling anyway, but the look in Dean's eyes said he would be gone the second the first ring sounded.

"Why are you here?" Cas asked, leaning into Dean's space as he always did so naturally. Dean said nothing, just met his gaze. "I missed you," Cas added simply.

"Yeah," Dean said quietly, and Cas had a feeling he was answering his question after all. "Come with me." Dean held out his hand. Cas had spent so much time following that man, through Heaven, Hell, purgatory, and into the passenger seat of a 1967 Chevy Impala, he didn't even know how to say no anymore.

They didn't talk as Baby ate up the miles of empty Midwestern highway, but Cas kept his eyes on Dean the whole time. His soul was damaged, but it wasn't broken, wasn't completely lost. It was dirty and tainted by the mark, but there were still glorious, glowing pieces of Dean left behind and Cas didn't want to miss a chance to watch them burning. If Dean noticed Cas was staring, he didn't react, focusing on the road.

It was evening, the skyline behind them on fire with reds and yellows, by the time Dean pulled over the car. A small town, a roadside diner like so many they had stopped in before. He finally looked over at Cas. "You're hungry, right?"

And Cas found that he was, his departing holiness leaving human needs like sleep and food in its wake. He nodded and Dean steered them inside, finding a booth and ordering burgers and beer.

"Where are we going?" Cas asked, fiddling with the corner of his paper menu. He thought briefly about going to the bathroom and calling Sam there, but talked himself out of it almost immediately. As much as he told himself that he'd never had a poker face around Dean, he knew it was mostly that he desperately didn't want to ruin this odd, unexpected moment.

Dean just shrugged, but he smiled and bumped his foot against Cas's under the table. "Hey remember that time we saved that waitress in Iowa by that weird bowling alley and she tried so hard to get your number?"

The angel smiled. "I remember everything, Dean."

After dinner Dean kept the drinks coming, reminiscing and chatting like nothing had changed. He carefully avoided talking about Sam, mostly focusing on things he and Cas had done alone. "You scared the shit out of me showing up in that barn, you know. All shadow wings and holy power. I don't really remember when you stopped being one of them and started being mi – just Cas."

"I was always yours, Dean." Cas finished the sentence Dean couldn't. "And you always knew it."

Dean laughed affectionately at that and slid out of the booth, grabbing Cas's sleeve and dragging him up on the rickety stage where a few drunk teens and nervous first dates had been enjoying the karaoke machine. Sufficiently lubricated with bourbon, Dean belted out a rather startling rendition of Aerosmith's "Angel" followed up by Cas's actually, rather good "Happy". The spartan crowd liked Cas so they sang "Kung-Fu Fighting" together, rounding out Dean's one-hit-wonder collection, before tossing cash on their table and tumbling out into the night.

The sun had fully set and the tiny town glowed against the deep black of summer night. Dean led Cas back to the car but only drove about ten minutes out of town before pulling over into a field and urging Cas out of the car. Cas felt warm and dopey, the alcohol affecting him in a way it never had when he was all angel.

Dean showed Cas how to climb up on the hood and lean back against the windshield so they could look up at the stars. They were both silent for a long time, taking in the vastness of the sky above them.

"What's it like?" Cas asked quietly.

Dean stretched his arms up to cup his hands behind his head, exposing a strip of skin above his waistband. "I dunno how to describe it. I still feel like me, but everything's kinda simpler. I don't really think I understand guilt, but I know I used to. It's kinda like being on really good painkillers, Cas. Everything seems easy. It feels okay to want things again, and not care about the consequences."

Dean glanced over to find Cas was no longer looking at the stars, but had his eyes fixed on Dean's face. They were still for a moment until Cas suddenly lurched forward, his hands clenching and releasing as another coughing fit tore through him.

"Are you really dying?" Dean asked quietly.

Cas just nodded.

Dean sat up suddenly and slid off the hood. "We should go." He came around to the passenger side and helped Cas jump off Baby without scratching her precious paint. "I'll bring you back to the hotel."

"Dean." The way Cas said his name was so plain and small, and yet it had the power behind it to stop a train. It certainly stopped Dean every time. He turned back and tipped his head questioningly at Cas, waiting for him to go on. "I saw this movie once at one of your hotels. It was called the Bucket List."

Dean couldn't help but smile. "You got something you wanna check off before you kick it, Cas?"

"Yes," Cas said simply and reached out, grabbing the front of Dean's jacket, pulling the taller man bodily against him and pressing their mouths together. There was no tentative brush of lips or soft testing of tongues; the kiss was hot, hard and sure. Dean braced his hands against the side of the car, trapping Cas against the window. Cas's fists relaxed, releasing his jacket then sliding down to paw at the hunter's sides and stomach, pull at his shirt, urge him to press closer.

When Dean finally pulled away and sucked in a breath he gaped at the panting angel between his arms. "Jesus Christ. Did you learn that from the pizza man too?"

"Among other things," Cas deadpanned. "And don't take the Lord's name in vain."

"Fuck," Dean breathed out against the angel's lips. Cas pulled him back in again desperately, while Dean's hand scrambled blindly for the door handle. Opening the back door he grabbed Cas and spun them around, tipping backwards onto the leather bench seat and pulling Cas down on top of him.

Dean slid a hand up under Cas's shirt, running his nails along any skin he found, his fingers skirting carefully around the Enochian words branded across his side, but seeking out every other inch of him. His other hand fisted in Cas's hair, guiding their lips back together so he could lick up into Cas's mouth hungrily. This was nothing at all like Cas's time with April, all gentle kisses and tentative hands. This was frantic and dangerous and exactly the way it should be.

Cas eventually pulled away to run sharp teeth down Dean's neck, inexperience forgotten as instinct took over, and Dean's hands became more eager in their search for new, bare skin. Cas's leg slipped between Dean's and he gasped when Dean ground up against him in response.

Dean fumbled against zippers and buttons, fighting a losing battle against the distraction of Cas's mouth and hands until enough clothing was shoved aside to take them both in hand. Cas sucked in a sharp breath at the new sensation, rocking into Dean's hand and crying out at the impossible feeling it sent shooting up through his gut.

While Cas's receding grace was painful, it also left a space for more human things to seep in. The ache in his chest and his heart was in sharp contrast to the building fireworks of pleasure Dean's hands were setting off in him. Set alight by the arousal that was curling soothingly around his weakening soul, Cas's grace stretched out, fizzing and popping as it touched the stark, black wall that was Dean's darkness. The combination of pain as an angel and pleasure as a human was quickly winding Cas up into a frenzy even he didn't fully understand.

Cas could feel that Dean too was caught in tortuous ecstasy. The demon in him was calmed and sated by the glide of Cas's hands under his t-shirt, while at the same time the Mark burned hot against the pressure of Cas's seeking grace. Dean's breath was coming out in short gasps that sounded like Cas's name more often than not.

Dean was wrapped around him, body and soul, and Cas barely even felt present anymore in his own vessel as he and Dean dizzily climbed the peak to release, finally finding it only moments apart.

They lay uncomfortably wrapped around each other in the back seat for a long time, maybe drifting in and out of sleep, Cas wasn't sure. When the darkness around them began to thin, ready to give way to dawn, Dean gently rolled Cas onto the seat, wrapped his trench coat around him and slipped out of the car. He climbed back up front and tucked one of his tapes into the stereo, familiar strains of old rock songs soothing Cas back into slumber.

When he woke again they were parked outside the hotel. Baby's engine was quiet and the car was cool; Cas didn't know how long they had been sitting there. His eyes flicked up to the rear view mirror and there was Dean's soft, green gaze, just watching him.

They piled out of the car and Dean pressed up against Cas, straightening his jacket and redoing a few buttons that had been mismatched in their half-hearted attempt to re-dress earlier. When Cas caught his eye, Dean just grinned. He led them into the hotel and up the stairs to the second floor.

"Dean?" Cas asked, a hint of teasing in his voice. "Is this what they mean by a 'walk of shame'?"

Dean turned down the hall, chuckling, and bumped straight into Crowley. The demon king stared at them both for a moment, clearly startled. Cas watched Dean attempt to school his grin into a more serious expression, but when Cas tucked up behind him, standing close enough that their arms pressed together, his smile struggled not to be suppressed.

"What do you want, Crowley?" Dean growled at him, the demon inside flaring up again to lick at Dean's edges.

Crowley's eyes slid to Cas and his eyebrow raised. "Castiel," he drawled, "you're looking...shabby." Dean's hands clenched into fists, but he didn't move. "You know, Sweetheart," the demon's gaze flicked back to Dean, "it was just a little fight. You don't have to hurt me by coming home smelling like angel."

"Shut up, Crowley," Dean spat. "I'm not interested in being the Luke to your Vader. You want to rule the galaxy, go find someone else."

Crowley's jaw tensed and his voice dropped from taunting to threatening. "If you don't feed that mark, it'll swallow you whole. Only I can give you what you crave. You can't fight this, Dean, the Mark has already won. You and I have work to do."

"I don't have shit to do, Crowley. And I'm done howling when I say I'm done. You want to go take back Hell, be my guest," Dean spread his arms wide, leaning over to half-step between Crowley and Cas, "but you're not the boss of me."

Crowley let out a huff of annoyance and stalked off, muttering under his breath as he stepped past them, "You'll come around."

Dean's eyes followed Crowley down the hall and around the corner, his forehead furrowed with concern. "I've got to go."

"Dean -" Cas started, but Dean cut him off with a look and a hand on his arm. He pushed open the hotel room door, pulling Cas in after him. Before Cas could begin to speak again, or even really find his balance, Dean was crowding him up against the wall, pressing their bodies flush and sucking Cas's bottom lip between his own.

Cas's breath caught and he willed his cough to hold off – he didn't want to ruin this kiss for anything. Too quickly Dean pulled away again, releasing the hands Cas hadn't even realized had been fisted in the sleeves of his trench coat.

"I'll see you soon," Dean promised before whisking out of the room and out of sight.

And even with this borrowed grace burning a hole in his soul, and the Mark ripping Dean's humanity into shreds, even with Crowley, and the angels, and Sam's demon murders, even with all that, Cas believed him.


End file.
